Leptospirosis, a bacterial infection people catch from water or soil contaminated with the urine of infected animals, has sickened 11,965 people in the Philippines this year as of Sept. 23, according to the Department of Health. That is 46% more than the 8,189 cases recorded over the same period in 2025, The Philippine Star reported.

The surge followed weeks of torrential monsoon rains and massive flooding, including in Metro Manila and Central Luzon. People who wade through that water, especially with cuts or scrapes, face the highest risk.

There are early signs the wave may be easing. The health department counted 3,284 cases from Aug. 27 to Sept. 9, a 1% drop from 3,330 cases in the preceding two weeks, and described the trend as a plateau. Despite possible reporting delays, the department said, "the observed decline in cases may signal that the current surge is easing," according to SunStar.

A Season That Turned on the Floods

The year did not start this way. As of Aug. 22, the cumulative case count was 37% lower than at the same point in 2025, even as infections were climbing during the height of the flooding, Health Secretary Edwin Mercado told DZRH.

The numbers then climbed quickly. Between Aug. 9 and Aug. 22, the department logged 2,374 cases, a 332% jump from the 550 cases recorded from July 26 to Aug. 8, The Philippine Star reported earlier. By Sept. 5, the country had recorded 8,317 cases, 14% more than a year earlier. The National Capital Region had the most cases, followed by Central Luzon and Calabarzon, and 81% of patients were male.

Deaths have run below last year's. The department reported 457 leptospirosis deaths as of Sept. 5, 41% fewer than the 772 recorded over the same period in 2025. As of Sept. 23, the cumulative case fatality rate stood at 5.08%, compared with 10.53% last year.

Hospitals felt the pressure. In late August, Mercado said San Lazaro Hospital in Manila was operating at up to 500% of its emergency room capacity and had set aside 120 beds for leptospirosis patients, and the National Kidney and Transplant Institute temporarily limited walk-in admissions after reaching full bed capacity.

Rats, Floodwater, and a Fast-Moving Infection

Leptospirosis is caused by Leptospira bacteria, which are carried by infected animals and shed in their urine. Rats are a major source in cities, and the health department also cites pigs. During heavy rain, urine in soil and on streets washes into floodwater, and people can be infected through contact with that water, especially through cuts in the skin, or by drinking contaminated water.

According to U.S. Centers for Disease Control and Prevention flood guidance, leptospirosis cases can rise after hurricanes, heavy rain, and floods, and people should watch for symptoms for two to 30 days after a flood. The Philippine health department lists fever, vomiting, nausea, muscle pain, headache, and reddish eyes among the symptoms. Severe cases can damage the kidneys and liver and can be fatal.

Speed matters. The department said "treatment must be initiated even without the laboratory confirmation" when leptospirosis is clinically suspected, because delays can rapidly lead to complications, including death.

Dengue Falls as Leptospirosis Rises

The picture for dengue, the mosquito-borne virus that usually dominates the Philippine rainy season, looks different. Cumulative dengue cases reached 168,060 as of Sept. 23, a 30% drop from 239,001 in the same period last year. The department reported 656 dengue deaths, 28% fewer than last year's 910, and 312 of those deaths, about 48%, were clinically classified as severe dengue. Students were the most affected group.

Dengue is not in retreat everywhere, though. The department recorded 21,122 dengue cases in the most recent three to four weeks, an 8% increase over the 19,572 cases in the previous comparison period.

Floodwater spreads leptospirosis directly, while water left standing after rain gives mosquitoes places to breed. Officials have not explained why dengue has lagged in 2025 while leptospirosis surged.

Floods, Climate, and Lessons for U.S. Communities

Flood-linked leptospirosis outbreaks are not unique to the Philippines. After Hurricane Fiona inundated Puerto Rico in 2022, the average weekly number of leptospirosis cases over the following 15 weeks was 3.6 times as high as before the storm, according to a CDC outbreak report. The report attributed the increase to a combination of exposure to contaminated water and increased testing. Puerto Rico reports more leptospirosis cases each year than any other U.S. jurisdiction.

This season's Philippine flooding came from monsoon rains. Scientists broadly expect a warming climate to make heavy rainfall more intense in many regions, but no attribution study has examined whether climate change worsened these specific floods, and Nature World News is not drawing that conclusion.

For anyone in a flood zone, the CDC's core advice is the same: do not wade in, bathe in, or swallow floodwater that may be contaminated, cover cuts with waterproof bandages, wear waterproof clothing and footwear near contaminated water or soil, and boil or treat water before drinking. The Philippine health department advises anyone exposed to floodwater to seek medical advice promptly, with or without symptoms. People should not take antibiotics without a doctor's guidance.

Anyone who develops fever, muscle pain, or red eyes in the weeks after flood exposure should see a doctor and mention the exposure. The department has warned that a new wave of cases can follow about two weeks after major flooding, and its coming epidemiological updates will show whether the recent plateau holds.

What Readers Want to Know

How many leptospirosis cases has the Philippines reported in 2026?

The Department of Health reported 11,965 cases as of Sept. 23, 2026, which is 46% higher than the 8,189 cases over the same period in 2025.

How do people catch leptospirosis?

People are infected through contact with water or soil contaminated with the urine of infected animals, often rats, especially through cuts in the skin. Wading through floodwater is a major risk.

Is the outbreak getting better?

The latest two-week data showed a 1% decline, from 3,330 to 3,284 cases, which the health department said may signal the surge is easing. Reporting delays mean the trend could change.

How many people have died?

The department reported 457 leptospirosis deaths as of Sept. 5, and a cumulative case fatality rate of 5.08% as of Sept. 23, lower than last year's rate.

What happened with dengue?

Dengue cases fell 30% to 168,060 compared with the same period in 2025, with 656 deaths, though cases rose 8% in the most recent three to four weeks.

Can leptospirosis occur in the United States?

Yes. Cases can rise after hurricanes and floods, as happened in Puerto Rico after Hurricane Fiona in 2022, according to the CDC.